1. Field of the Invention
The present invention relates to an apparatus for forming a sheet of material and cutting individual portions of the material from the sheet. More particularly, the invention relates to an apparatus for forming a sheet of dough material, e.g., masa (corn-based dough), and cutting individual portions or chips from the sheeted dough.
2. Description of Relevant Art
Apparatus for forming sheets of various materials, including dough or the like food products, which force the material through a gap or nip located between a pair of rotating rollers are well known in the art. In such apparatus, the supply of dough is positioned above the gap formed between the confronting rollers, a dough mass is forced into the gap, and the rollers form the dough into a sheet. The sheet then is cut or suitably portioned, and the portions are then processed according to the desired product. For example, in the case of snack foods, the cut portions are baked or fried, seasoned, etc.
Various problems exist in the production of sheeted materials using the aforementioned apparatus. For example, the thickness of the final product (which may be, e.g., tortilla chips), strongly influences the product attributes that are important to consumers. In other words, a product that is too thick typically is unacceptable or unsatisfactory to consumers.
In the prior art dough-sheeting machines mentioned above, variations often are present in the rheology of the dough or masa mass that is fed into the gap between the rollers. Such variations may exert substantial pressure on the rollers and cause the framework which supports the rollers to deflect, resulting in changes in roller gap size, which in turn result in variations in the thickness of the sheet and thus the final product. At present it is not practical to directly measure the thickness of the sheet output by the rollers. This problem currently is handled by a sheerer apparatus operator who monitors such deflections and manually adjusts the position of one of the rollers. These manual adjustments typically are required about 20-30 times during a seven hour period. In addition, manual adjustment of the roller gap size is unsatisfactory in that this method yields products about 30% of which are down-graded by consumers as being too thick. Accordingly, there is a need in the art for an apparatus and method for producing sheeted materials having a uniform thickness.
The dough sheet formed by the rotating rollers as described above is subjected to a cutting procedure in which individual portions of dough are cut from the sheet. Specifically, a rotating cutter typically is positioned so as to press against the surface of one of the rollers. As the dough sheet adheres to the roller, the exterior surface of the cutter, which is configured to cut-out the portions in a desired shape, engages the dough sheet and cuts such portions from the remainder thereof. A stripper wire assembly then separates the cut-out portions which are carried by a conveyor or run-out table to the next processing stage.
The length of the rollers which sheet the dough in the aforementioned apparatus may be around three feet, e.g., 39 inches, and thus produce a three foot wide dough sheet. However, some applications utilize longer rollers, e.g., 46 inches, which produce wider sheets of dough. In any event, the cutter used with such apparatus has a length corresponding to that of the rollers (as the exterior surface of the cutter presses against the dough sheet adhering to the roller). The considerable length of the cutter causes several problems.
In order to adequately cut the dough sheet carried by the one roller, the cutter must be pressed against the roller over the entire length thereof. Furthermore, the pressure exerted by the cutter against the roller must be uniform over its length to produce even and uniform product portions. The cutter has opposite ends which are journalled in bearings disposed outside the cutter portion which engages the roller. Force is applied against the bearing housings by air cylinders or springs to lift or press the cutter against the roller. However, because of the considerable length of the cutter, the forces applied to or adjacent the ends thereof cause bowing at the central portion thereof. More particularly, the bowing reduces pressure and cutting effectiveness at the center of the cutter.
In prior art apparatus, some cutters are crowned (formed with a special profile at the center) to compensate for the aforementioned bowing. However, the amount of crowning is determined by a trial and error process and does not always yield successful results. In addition, the cutter must be re-machined periodically to account for wear of the special profile or to permit its use for new applications. Further, the cost of the cutter is increased due to the special machining necessary to form the profile.
Another prior art solution to the problem of cutter bowing, particularly if the cutter length exceeds 30 inches, is to provide center supports that press the center of the cutter against the roller. This solution, however, is unacceptable in that the center supports require frequent maintenance and add to the complexity of the apparatus. In addition, such inboard center supports reduce the effective area for forming product, and thus, increase the amount of lace (i.e., recycled masa returned to the dough mass supplied to the roller gap). Accordingly, there is a need in the art for an improved cutter assembly for a sheeter apparatus.